Vacuum-type infusion brewing has been known for years in making coffee and other infusions, but has met limited success commercially due to several drawbacks. In summary, vacuum-type coffee brewing typically involves a device which has a lower vacuum chamber, and an upper steeping chamber with a filter therebetween. In use, coffee particles are let to steep in hot water in the upper chamber, during which time both the coffee particles and water are kept from proceeding to the lower chamber by the filter. After a given steeping time has been reached, the pressure in the lower chamber is lowered, i.e. a so-called “vacuum” is made, which draws the infusion through the filter and into the lower chamber.
To create the vacuum, a first known method is to use a piston which is lowered in the vacuum chamber. This has the drawback of involving many moving parts and is typically limited to providing beverages of a single given volume, associated to the stroke of the piston.
Another method is to use a vacuum pump. This second method can eliminate the need for the piston and allow more flexibility in the volume of the brewed beverage. However, it had a recognized drawback that a substantial amount of liquid reached the area adjacent the inlet and was is aspired by the vacuum pump. The liquid either came from upper chamber dripping, or from condensation occuring on the walls of the lower chamber, for example.
Several suggestions have been made in the past to deal with this drawback, which, although satisfactory to a certain degree, have met limited success. For instance, Suzuki et al., in U.S. Pat. No. 5,297,472, show a downwardly oriented vacuum inlet adjacent the wall of a vacuum chamber. Yet, drops nevertheless accumulated under the downwardly oriented tip of the vacuum inlet and a substantial amount of liquid was nevertheless aspired. By consequence, Suzuki et al. taught using a relatively complex and costly system to deal with the substantial amount of aspired liquid.
There thus remained room for improvement.